1. Field of the Invention
The present invention relates to a stator constituting a stator of a motor for driving to rotate a record medium of HD (hard disk) or the like, a motor having the stator and a record medium drive apparatus having the motor as well as a method of fabricating a stator.
2. Description of the Related Art
In recent years, an information recording/reproducing apparatus using a hard disk drive apparatus (HDD) has been started to be adopted in a portable music reproducing apparatus, a portable telephone or the like. Particularly, an information/recording reproducing apparatus of a portable type is going to constitute a main current in the future owing to its availability, and further small-sized formation and thinned formation have been requested. In accordance therewith, an improvement has been carried out for small-sized formation and thinned formation of a motor for driving HD (hard disk).
Here, a brief explanation will be given of a hard disk drive apparatus having a general motor in reference to FIG. 27 through FIG. 29. As shown by FIG. 27, the disk drive apparatus 40 includes a stator 43 having a coil 41 and a stator core 42, and a rotor 46 having a permanent magnet 44 and a hub 45. The hub 45 is supported by a sleeve 47 rotatably around an axis line L and formed with a fitting portion 45a fitted to a center hole of a disk D. Thereby, the hard disk D is fixed to the hub 45. Further, an outer periphery of the hub 45 is fixed with the permanent magnet 44 to be opposed to the stator core 42 to be spaced apart from each other by a predetermined distance.
The sleeve 47 is fixed to a base 48 and rotatably supports the hub 45. In this case, a more or less gap is ensured between the sleeve 47 and the hub 45, and the gap is filled with oil W. Further, an outer surface of the hub 45 or the sleeve 47 is pertinently formed with a radial dynamic pressure generating groove and a thrust dynamic pressure generating groove, not illustrated, referred to as a herringbone groove. Thereby, when the hub 45 is rotated around the axis line L, the hub 45 is rotated stably without being fluctuated in a thrust direction and a radial direction. That is, the hub 45 is brought into a state of being supported by a hydraulic dynamic bearing.
As shown by FIG. 28, the stator core 42 includes a core back 42a formed in a ring-like shape, and a plurality of teeth 42b formed to extend in a radius direction. Further, the stator core 42 is supported by a base 48 on a side of the core back 42a. The teeth 42b are formed at respective predetermined angles around the axis line L and formed such that a number (slot number) thereof constitutes a multiple of 3. For example, the teeth 42b are formed by 9 slots at respective 40 degrees. Further, the coils 41 are respectively wound at surroundings of the plurality of teeth 42b. In this case, the coils 41 are wound at every 3 (spaced apart by 2) thereof to constitute 3 phases (U phase, V phase, W phase).
When the hard disk D is driven by the disk drive apparatus 40 constituted in this way, first, the coil 41 is supplied with a three phase alternating current to generate a magnetic field in the coil 41. The magnetic field is operated to the permanent magnet 44 by way of the teeth 42b to rotate the rotor around the axis line L. Thereby, the disk D fixed to the rotor 46 by the fitting portion 45a can be rotated.
Meanwhile, as described above, further small-sized formation and thinned formation are requested for the motor in the future. However, as shown by FIG. 29, the coil 41 is wound at the surrounding to the tooth 42b by a predetermined turn number in order to ensure a constant electromotive force, and therefore, a thickness T1 is necessarily thickened. Therefore, it is difficult to achieve thinned formation as a whole. Particularly, the thickness T1 of the coil 41 is significant in comparison with the product constituted otherwise, and therefore, the thickness T1 effects a considerable influence on thinned formation. Therefore, in order to realize thinned formation, it is necessary to thin the coil 41 as thin as possible. However, as described above, the predetermined turn number is needed for ensuring the constant electromotive force, and therefore, the turn number of the coil 41 cannot simply be reduced.
Hence, although there is conceivable a method of reducing the turn number of the coil 41 wound per the single tooth 42b by increasing the number (slot number) of the teeth 42b, in this case, as shown by FIG. 28, with an increase in the slot number, a distance T2 between the teeth 42b is reduced. Here, in order to wind a coil wire around the tooth 42b, the coil wire is normally wound there around by inserting a coiling machine between the teeth 42b and orbiting the coiling machine centering on the tooth 42b. Therefore, when the distance T2 between the teeth 42b is made to be smaller than a rectified value, the coiling machine cannot be made to pass therethrough and the coil wire cannot be wound therearound. Therefore, the slot number cannot be increased to a necessary number and the number is limited. Therefore, the more amounted to the thinned formation of the total, the more difficult to thin the thickness T1 by extremely reducing the turn number of the coil 41 for the single tooth 42b. 
On the other hand, there is known a disk drive apparatus achieving thinned formation as a whole by constituting a stator without mechanically winding a coil wire therearound (refer to, for example, Patent References 1 and 2).
As shown by FIG. 30 and FIG. 31, the disk drive apparatus 50 includes a metal core board 51 having a function of a core and windings of a motor and a function of a wiring board mounted with a part of IC or the like. The metal core board 51 constitutes a stator and is constituted by a tooth connecting portion, not illustrated, a tooth coil forming portion 51a, a tooth front end portion 51b, a wiring 51c and a through hole 51d. 
The tooth connecting portion is constituted by laminated plates of thin plates and formed by a ring-like shape. The tooth coil forming portion 51a is a portion a base end side of which is fixed to the tooth connecting portion and which is formed by being extended to an inner side in a radius direction, and a portion in correspondence with the tooth of the background art. Normally, the tooth coil forming portion 51a is formed to constitute a number of pieces 1.5 times as much as a number of poles of a permanent magnet 52 formed in a ring-like shape. Further, a front end of the tooth coil forming portion 51a constitutes the tooth front end portion 51b to be opposed to the permanent magnet 52.
The wirings 51c are arranged at a surface and a rear face of the tooth coil forming portion 15a and is fixed by an insulating resin 53. Further, the insulating resin 53 is formed with the through hole 51d an inner face of which is plated by a metal and which electrically connects to the wirings 51c formed at the surface and the rear face. At this occasion, as shown by FIG. 31, the wirings 51c and the through holes 51d are connected to spirally surround the tooth coil forming portions 51a. Thereby, by making an electric current flow in the wiring 51c, a magnetic field for rotating the permanent magnet 52 can be generated.
According to the disk drive apparatus 50 including the metal core board 51 constituted in this way, the stator can be constituted without winding mechanically the coil wire around the tooth as in the related art, and therefore, the number of the tooth coil forming portions 51a, that is, the slot number can be increased without being conscious of the coiling machine. Therefore, the wiring 51c wound at the surrounding of the single tooth coil forming portion 51a can be reduced, and a thickness can be restrained as less as possible. Therefore, thinned formation as a whole can be achieved.
Patent Reference 1: JP-A-2004-23935
Patent Reference 2: JP-A-2004-32926
However, according to the related arts described in Patent References 1 and 2, the following problem still remains.
That is, since the insulating resin 53 is interposed between the tooth coil forming portion 51a and the wiring 51c, in comparison with the case of winding the coil wire, a total length thereof is prolonged. Further, the through hole 51d is bored by mechanical working or laser working, and therefore, a positional shift thereof with the wiring 51c is liable to be brought about. Therefore, it is difficult to arrange the through holes 51d by narrow intervals and the total length is further prolonged. As a result thereof, there is brought about a drawback that an electric resistance is increased, an efficiency of the electromotive force is deteriorated and power consumption is increased.
Further, owing to a structure in which a portion of the wiring 51c and the tooth coil forming portion 51a are embedded at inside of the insulating resin 53, there is a concern that heat generated by electricity conduction is not radiated to outside but is confined to inside. Therefore, exfoliation of a part is liable to be brought about, which amounts to a reduction in a power function and a reduction in a reliability.
In this way, even when the thinned formation can be achieved, a new drawback is brought about as a substitute therefor.